1. Field of the Invention
The present invention relates to a container device used for a source of a liquified gas, and, more specifically, to a container device having an out-take pipe mechanism, and which is used in a semiconductor production step.
2. Description of the Related Art
Liquid material gasification control devices (called "baking systems" hereinafter) having a mechanism for gasifying a liquid gas so that it can be handled as regular gas, have hitherto been used in a semiconductor production apparatus as prestage equipment to a CVD (chemical vapor deposition) reaction furnace. FIG. 1 shows an example of the main structure of such an apparatus. As shown in this figure, the baking system 1 includes a constant temperature room 2, a tank 3, a flow controller 4, and a pneumatic valve 5. A source liquid container device 6 of the type most often employed supplies a liquid material into the system 1.
The source liquid container device 6 includes a main body 7, a gas supply line 8, a source liquid delivery line 9, a gas supply valve 10, a liquid delivery valve 11, and the like. The container device 6 is connected by a joint 12 to the system, and can be removed therefrom. A gas supply company fills the container device 6 with a source liquid 13, using a method similar to that used in the case of regular gases, and supplies the gas-filled container to a semiconductor maker.
To transfer the source liquid, a purge valve 14 is closed, and the gas supply valve 10 and the delivery valve 11 are opened. Then, a compressed inert gas is introduced into the main body 7, through the gas supply lines 15 and 8, causing the source liquid 13 to flow via pipes 9 and 16 into the tank 3 of the baking system. At this time, the tank 3 is in an unpressurized state.
The source liquid is then gasified in the tank 3 by using the constant temperature room 2, the gasified source passes through the flow controller 4, and is drawn into a reaction furnace through a gas line connected to the furnace.
An example of the source liquid 13 which is used in this method, is an organic source liquid such as tetraethoxysilane Si(OC.sub.2 H.sub.5).sub.4 (to be abbreviated to TEOS hereinafter) to form an insulation layer on a semiconductor substrate. In certain cases, an organic source liquid containing a doping material such as phosphor (P), boron (B), arsenic (As), or the like is used to form a film which includes impurities to be diffused in a semiconductor substrate.
To replenish the tank with the source liquid 13, usually, the container device 6 is removed from joint 12 as mentioned before, and sent to the gas supply company for replenishment. Consequently, the connection pipes 15 and 16, and those sections of the lines 8 and 9 which are located between the joints 12 and the valves 10 and 11 of the container device 6 are brought into direct contact with the atmosphere every time the tank is replenished.
In the meantime, just after the source liquid is transferred, some of the source liquid still remains on the inner surface of the connection pipe 16 and the like. The organic source liquid used in this method reacts, though moderately, with moisture in the atmosphere to produce byproducts such as silica (SiO.sub.2).
The prior art was designed to avoid the problems associated with the remaining of liquid. To remove the remaining liquid, the purge valve 14 is opened and the valves 10 and 11 are closed to flow an inert gas through the connection pipe and the like to carry out purge drying both before and after transferring the source liquid. However, with this prior art, it is very difficult to perform perfect purge drying because the pipes 15 and 16 which continue from the purge line (the line for a purge gas) to the valves 10 and 11, are too long, and they are not designed for making a purge gas to flow. If purge drying is not complete, the byproduct such as silica is produced on the inner surface of the connection pipe 16, the valves 10 and 11, and the like, as stated before. This byproduct contaminates the container device 6, the baking system 1, and a to-be-processed material. Further, it is likely to be mixed into the liquid in the tank 3 in the baking system 1, causing failure of the flow controller 4. In the case of handling a source liquid containing a doping material such as phosphor or arsenic, an incomplete purge causes generation of a poisonous gas with irritating smell, which affects human health. Therefore, the purge operation must be carried out very carefully.
As described, both before and after transferring the source liquid to the baking system, the source liquid remaining on the inner surfaces of the connection pipe connected to the system, and of the line of the container device must be completely removed by the purge drying. However, the complete purge effect cannot be obtained in the conventional source liquid container device; therefore the container device itself and the baking system are contaminated, affecting the quality of a to-be-processed substrate such as a wafer. Further, with the conventional container device, very special attention must be paid in order to operate the system in safety when handling a source liquid containing a poisonous substance such as phosphor, arsenic or the like.